1. Field of the Invention
The present invention relates to a control unit for an electric power steering device, and more particularly, to a control unit for an electric power steering device for assisting the steering of a steering wheel based on a detection value of a magnetostrictive torque sensor.
2. Description of Background Art
Electric power steering devices are known for detecting with a torque sensor the twisting torque generated in a steering shaft to assist steering of a steering wheel with an electric motor according to the twisting torque. Such electric power steering device is commonly controlled by a control unit (ECU) of a vehicle.
This type of electric power steering devices include the electric power steering device in which a magnetostrictive torque sensor is used as the torque sensor. See, for example, JP-A No. 2008-83063. The magnetostrictive torque sensor is configured with a magnetostrictive film formed on a surface of the steering shaft and a detection coil provided around the magnetostrictive film. This sensor can be made relatively compact, and therefore has the advantage of contributing to the miniaturization of the vehicle.
Since the magnetostrictive torque sensor is subjected to a bending load, it is necessary to provide plural bearings to reduce bending. However, this causes upsizing of the device and an increase in the production cost.